2,541 research outputs found
Vacuum interpolation in supergravity via super p-branes
We show that many of the recently proposed supersymmetric p-brane solutions
of d=10 and d=11 supergravity have the property that they interpolate between
Minkowski spacetime and a compactified spacetime, both being supersymmetric
supergravity vacua. Our results imply that the effective worldvolume action for
small fluctuations of the super p-brane is a supersingleton field theory for
, as has been often conjectured in the past.Comment: 8p
Zero Modes for the D=11 Membrane and Five-Brane
There exist extremal p-brane solutions of supergravity for
p=2~and~5. In this paper we investigate the zero modes of the membrane and the
five-brane solutions as a first step toward understanding the full quantum
theory of these objects. It is found that both solutions possess the correct
number of normalizable zero modes dictated by supersymmetry.Comment: Minor typos corrected, one reference added, agrees with published
version. 9 RevTeX pages, 1 figure include
Scattering of Fermions off Dilaton Black Holes
We discuss how various properties of dilaton black holes depend on the
dilaton coupling constant . In particular we investigate the -dependence
of certain mass parameters both outside and in the extremal limit and discuss
their relation to thermodynamical quantities. To further illuminate the role of
the coupling constant we look at a massless point particle in a dilaton
black hole geometry as well as the scattering of (neutral) fermions. In this
latter case we find that the scattering potential vanishes for the zero angular
momentum mode which seems to indicate a catastrophic deradiation when .Comment: 12, Oslo-TP-4-94, USITP-94-
Small Orbits
We study both the "large" and "small" U-duality charge orbits of extremal
black holes appearing in D = 5 and D = 4 Maxwell-Einstein supergravity theories
with symmetric scalar manifolds. We exploit a formalism based on cubic Jordan
algebras and their associated Freudenthal triple systems, in order to derive
the minimal charge representatives, their stabilizers and the associated
"moduli spaces". After recalling N = 8 maximal supergravity, we consider N = 2
and N = 4 theories coupled to an arbitrary number of vector multiplets, as well
as N = 2 magic, STU, ST^2 and T^3 models. While the STU model may be considered
as part of the general N = 2 sequence, albeit with an additional triality
symmetry, the ST^2 and T^3 models demand a separate treatment, since their
representative Jordan algebras are Euclidean or only admit non-zero elements of
rank 3, respectively. Finally, we also consider minimally coupled N = 2, matter
coupled N = 3, and "pure" N = 5 theories.Comment: 40 pages, 9 tables. References added. Expanded comments added to
sections III. C. 1. and III. F.
Supersymmetry Enhancement of D-p-branes and M-branes
We examine the supersymmetry of classical D-brane and M-brane configurations
and explain the dependence of Killing spinors on coordinates. We find that one
half supersymmetry is broken in the bulk and that supersymmetry near the
D-brane horizon is restored for , for solutions in the stringy frame,
but only for in the10d canonical frame. We study the enhancement for the
case of four intersecting D-3-branes in 10 dimensions and the implication of
this for the size of the infinite throat of the near horizon geometry in
non-compactified theory. We found some indications of universality of near
horizon geometries of various intersecting brane configurations.Comment: 18 pages, late
Twenty Years of the Weyl Anomaly
In 1973 two Salam prot\'{e}g\'{e}s (Derek Capper and the author) discovered
that the conformal invariance under Weyl rescalings of the metric tensor
displayed by classical
massless field systems in interaction with gravity no longer survives in the
quantum theory. Since then these Weyl anomalies have found a variety of
applications in black hole physics, cosmology, string theory and statistical
mechanics. We give a nostalgic review. (Talk given at the {\it Salamfest},
ICTP, Trieste, March 1993.)Comment: 43 page
Let's talk about varying G
It is possible that fundamental constants may not be constant at all. There
is a generally accepted view that one can only talk about variations of
dimensionless quantities, such as the fine structure constant . However, constraints on the strength of
gravity tend to focus on G itself, which is problematic. We stress that G needs
to be multiplied by the square of a mass, and hence, for example, one should be
constraining , where is
the proton mass. Failure to focus on such dimensionless quantities makes it
difficult to interpret the physical dependence of constraints on the variation
of G in many published studies. A thought experiment involving talking to
observers in another universe about the values of physical constants may be
useful for distinguishing what is genuinely measurable from what is merely part
of our particular system of units.Comment: 6 pages, Gravity Research Foundation essa
The Finiteness Requirement for Six-Dimensional Euclidean Einstein Gravity
The finiteness requirement for Euclidean Einstein gravity is shown to be so
stringent that only the flat metric is allowed. We examine counterterms in 4D
and 6D Ricci-flat manifolds from general invariance arguments.Comment: 15 pages, Introduction is improved, many figures(eps
Thermal divergences on the event horizons of two-dimensional black holes
The expectation value of the stress-energy tensor \langleT_{\mu\nu}\rangle
of a free conformally invariant scalar field is computed in a general static
two-dimensional black hole spacetime when the field is in either a zero
temperature vacuum state or a thermal state at a nonzero temperature. It is
found that for every static two-dimensional black hole the stress-energy
diverges strongly on the event horizon unless the field is in a state at the
natural black hole temperature which is defined by the surface gravity of the
event horizon. This implies that both extreme and nonextreme two-dimensional
black holes can only be in equilibrium with radiation at the natural black hole
temperature.Comment: 13 pages, REVTe
Higher Structures in M-Theory
The key open problem of string theory remains its non-perturbative completion
to M-theory. A decisive hint to its inner workings comes from numerous
appearances of higher structures in the limits of M-theory that are already
understood, such as higher degree flux fields and their dualities, or the
higher algebraic structures governing closed string field theory. These are all
controlled by the higher homotopy theory of derived categories, generalised
cohomology theories, and -algebras. This is the introductory chapter
to the proceedings of the LMS/EPSRC Durham Symposium on Higher Structures in
M-Theory. We first review higher structures as well as their motivation in
string theory and beyond. Then we list the contributions in this volume,
putting them into context.Comment: 22 pages, Introductory Article to Proceedings of LMS/EPSRC Durham
Symposium Higher Structures in M-Theory, August 2018, references update
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